1. Field of the Invention
The present invention relates to metal spot plating systems which allow a continuous web of metal to be selectively plated at regular and discrete intervals. More particularly, this invention relates to such a planing system in which the region to be plated can be varied with a minimum of retooling.
2. Description of the Prior Art
Integrated circuits are combinations of interconnected circuit elements housed in a suitable matrix and mounted of a metal plated pad. The manufacturing process for mass producing integrated circuits generally involves a step wherein many identical lead frames are covered or plated with a metal coating. Automated, selective plating systems, such as described in U.S. Pat. No. 3,723,283, have been developed which allow continuous strips or webs of lead frames to be passed through the system while selected areas on the lead frame are uniformly plated with metal. Much prior art has focused on optimizing various parameters of the automated electroplating process . U.S. Pat. No. 4,405,432, for example, teaches the use of a large planar electrode which results in faster and higher quality plating. U.S. Pat. No. 4,409,924 describes a plating apparatus which automatically aligns the web prior to plating.
A major problem with current selective plating systems is that extensive retooling of the system must be conducted whenever a new plating operation is undertaken. This retooling is necessary because plating systems of the prior art generally employ dedicated electrolyte delivery systems which are specifically designed for an individual job. In these systems, a mask containing a specific pattern of apertures is used to expose the individual regions of the web to be plated. Electrolyte solution is then injected at each mask aperture to accomplish the selective plating. Because of this configuration, retooling involves redesigning both the mask and the nozzle block which contains the electrolyte delivery system. The cost of retooling a selective plating system for a new job is a significant part of the total bid for the new project.
Another problem with selective plating systems of the prior art is that the rate at which the electroplating process occurs is limited by the rate at which used electrolyte solution can be removed from the plating area. This necessitates longer plating periods.